Combustion tube heating apparatus



July 8, 1952 E. A. comes` l 2,602,440

. coMBUsTIoN TUBE HEATING APPARATUS Filed sept. 2o, 194s 2 SHEETS-SHEET1 A JNVENTOR.

July 8, 1952 E. A. coRNs COMBUSTION TUBE HEATINGV APPARATUS 2SHEETS-SHEET 2 Filed Sept. 20, 1948 INVNTOR bw/N A. Coe/vs ATTORNEYS.

Patented July 8, 1952 COIVIBUSTI'ON TUBE HEATING y.APPARATUSEdwinACorns; Lakewood, hioassigv nor'to Lee WilsonRocky River, OhioApplication September 20, 1948;,.Se1ia1'Nm 50,061

8 Claims'. (C1. 126-91) l f This'invention relates' to furnaces,particularly industrial 'furnaces of ajkind sometimes usedl forannealing, providedI withv heating elements Aof the'radiant-tube type'.

In'the'past", industrial`V furnaceshave-been proposed'V4 emplciyingradiant-tube heating elements extending' transversely into; and evenentirely acrossI the` interior' of the furnace, therebycorrespondinglydecreasing the space-available for" the material to be,heat-treated; In' otherfinstances. elortshave been made to provideradiant-tube heatingelementsparalleling the side walls ofthe furnace.Inboth cases; difliculties'have.been'exu perien'ced in soarranging theparts; particularly theburner parts; as tof escape the; necessity forhaving' a plurality of4v openings' through the furnace'wallf.' one foreach' end of the heating element; in additionto which it has been foundnecessary toA usev supporting. hangers: or"V costly alloy metals. orrefractory supports interfering with heatltransier atthe supportingpoints. Also, expansion of the metal of. the heatingielement due to itschangingA temperature has required special. provisions, such as slidingjoints or seals,

to permit expansion without objectionable stress and distortionof theheating elements'.

' j The present invention resolves. these andzother difficulties bymeansA ofa'novel .constructionin which a heating element ofthe.radiant-tube type is employed which i'sformed'into a.closedverticalloop, the same. cooperatingA wtha fittingv obv-i'- ating the. need'.forsupporting.. means. located. insidethefurnace. and, requiring .butesingle openf ing'in the furnace Wall; Accordingly, the invenn tion maybesaid'tohave foritsprincipal objects .Y/ A

to provide simple, improved, more. efficient. in.n stallations -in which.closed-loop heating `elements ofthe. radiantftube .type are. employedvto decrease the number ofopenings in thefurnace walLand increasethespace available vwithinlthe furnace..

The invention lcomprehends. the constructions illustrated in Figures 1`to-6 of the` accompanying drawings, in which Figuren 1 shows la.vertical lsection, withparts in elevatiomofone preferred-em bodiment.ofthe invention; Figure 2LA is. asec-`V tional plan-correspondingtoFigure `1;. Figure 3 v isa-n.. elevation ofr the heating elementoffFigures 1 and2asY seen fromtherig-ht in Figure l; Figure lLis averticalsection, with parts ineleva-tion,

along lined-4- of Figure l-,butonanenlarged Y.

scale; Figure 5 is-a'verticalsection corresponding. toFigure 1V butillustrating. afsecondpreferred embodiment of. the nature-of amodification; and Figure 6is an elevation'of the heatingv element ofFigure 5as seenrfrom the left in Figure-5.v

The installation illustrated in Figureifl. makes use of anupright'peripheral portion-I' of. antan;- nealing furnace, whichportionmayv bel either an end wall or a sidewall, having.therein anopen;- ing 2 for a burner assemblyiwhich openingjis preferably slightlyflaredv at the endther'eof adjacentthe interior of the furnace. Insidethe furnace is a closediloop heating element. of: 4the radiantetubetype, the same being` generallyf oval in shape,l extending. normally toopening 2,'lying in aplane paralleling theupright portion off thefurnace, and conveniently comprising aplurality of parallel tubularmembersinterconnected by elbows as shown-in Figure 3.While'the-arrangement and proportions may vary widely,l the heatingelement shown extends on oppositev sides`A of the burner assemblyapproximately equardistancesV above and-below opening 2, is narrow inwidth in proportion to its length, and diminishes in crossV section froma maximum in the zone where` it receives incoming4 gases to a minimum inthe zonewhere it returns outgoing gases.

The ends. of the heating element 3 receiving incoming and returningoutgoing. gasesv are ,respectively designated 3a vand. 3b.

At one side of the oval, heating. element 3is connected to amultiple-,Wall fitting.. comprising part of the. burnerassembly. TheVlatter, lgenerally designatedlll, has portsat cacho-fthe. two ends ofthe fitting for incoming and., outgoing gases, the portsat the end ofthefitting@ adjacent the interior of the furnace communicating with ends.3aand 3b. of heating element. and those at the opposite end ofthe fitting,thatis. to say at the end thereof that projects out of .the furnace,communicating with a discharge stackv 5, an airv inlet conduit 5,.and agas inlet conduit. 1. The tting which, together with other elements,makes up burner assembly vcomprisesthree principal elements; viz., aninner cylindrical shell I I an outer cylindrical shellvIZ, thelatterincluding an annular closure welded in place at the end of thefitting which projectsout of thefurnace, and, welded toeither or toboth-of inner shell Il and outer shell I2', a. two-branch couplingmember I3 that-may conveniently be cast as an integralA unit; Branch |lofV coupling membery I3Viswelded to enda ofheating element 3f; branch|1319, to end 3b of the heating element.

vAs illustratednin Figures l and-3, coupling I3 is cutaway at anangle ofabout immediately below branch I3b, this in order to permit it-toreceive `atubular connecting member. ltwhich; at its outer. end,constitutes branchA l3ar-.of,coupling position as seen from either end.Thus there is' formed between inner shell and outer shell] I2 agenerally annular passage Il shown to best advantage in Figure 4 throughwhich passage products of combustion received from` end 3bI of heatingelement 3 by branch I3b of coupling member I3 can pass on their way todischarge stack 5. projects an igniter I8 which, as shown, takes theform of a spark plug. The latter may be mounted at any suitable placebut isvillustrated as located outwardly of the furnace between thefurnace wallfand the port in outer shell I2 communicating withdischargestack 5.

Projecting into inner shell II from the outer end thereof is a burnertube. 2| which is mounted in concentric relation to inner shell I I. Theend of burner tube 2| carries a burner nozzle 22, the latterbeingreceived within a supporting ring 23 retained in the desiredconcentric v:relation to inner shell Il by means of spacer 24 (Figure4). In the periphery of burner nozzle 22 .is formed a series of airpassages 25 which extend longitudinally of the nozzle within supportingring 23. The function of these air passages is to admit air to thecombustion zone.

Burner tube 2| is Welded to and carried by a flanged housing 3| which isremovably mounted, as by bolts, on a registering flange at the outer endof inner shell II; preferably, a suitable packing material, such as anasbestos gasket, is interposed between the two flanges. An adjustablecoupling 32 connected to gas inlet conduit 'I projects through housingSI into burner tube 2|, but is spaced therefrom to permit primary air topass between them. A series of ports 33`is provided in the inner wall ofhousing 3| to admit secondary7 air into the generally annular spaceA I5between burner tube 2| and inner shell Air linlet conduit 5 is coupleddirectly to housing 3| as indicated in Figure 1.

In placing the apparatus in use, gas is permitted to pass through gasinlet conduit I into burner tube 2|, thence into branch I 3a of couplingmember I3, thence into heating element 3, thence into branch |319 ofcoupling member I3, and thence into the generally annular passage I1between inner shell and outer shell I2. At this stage, the resultingmixture of air and gas is ignited by means of spark plug I8. The mixtureburns back through heating element 3 to burner nozzle 22, to whichadditional air is supplied in the meanwhile through air inlet 6. Part ofthe air so supplied passes through burner tube V2| as-previouslydescribed; another part passes through generally annular passage I6 intoair passages 25 in the periphery of burner nozzle 22; the remainderpasses through generally annular passage I6, around supporting ring 23,and into branch |3a of coupling member I3, where it mixes with gas andair issuing from burner nozzle 22.

In operation,l air passing through generally annular passage lf3 ispre-heated by products 'of Into this generally annular passagecombustion passing through generally annular passage I'| on their way todischarge stack 5.

The embodiment of the invention illustrated in Figures 5 and 6contemplates the installation, in an opening 2 in the wall of an indus*trial furnace, of a somewhat differently constructed multiple-shellfitting which, together with other elements, makes up burner assembly'4. As before,'the tting has separate ports for incoming and outgoinggases communicating at the inner end of the fitting with heating element3 and at the outer end thereof with air inlet conduit 6,. gas inletconduit 'I and discharge stack 5; In the embodiment of the inventionshown in Figures 5 and 6, unlike that shown in Figures 1 to 4, air inletconduit 6 takes the form of an air intake stack concentric with 'andsurrounded by discharge stack 5, thus permitting additional pre-heatingof the incoming air.

The fitting, which, with other elements, goes to make upl burnerassembly 4, comprises an inner shell 4| communicating directly with`airintake stack `6 and, surrounding'inner shell 4|, an outer shell 42,the latter carrying anl annular closure at the end thereof whichprojects from the furnace and terminating at its other end in atwo-branch coupling member 43. Branch 43a of coupling member 43communicates with end 3a of heating element 3; branch 43h, with end 3bof the heating element. Coupling member 43 is cut away as shown topermit it to receive an integral tubular connecting member 44 havingelbow 45 communicating with a generally annular passage 46 within innershell 4|. Between vinner shell 4| and outer shell 42, which, as

shown, are mounted in concentric relation` to each other, is a generallyannular passage 47 through which products of combustion received fromend 3b of heating element 3 through branch 43h of coupling member 43 aretransmitted to the annular space 48 between air intake stack 6 anddischarge stack 5.

If desired, a park plug (not shown) may be provided as in theinstallation illustrated in Figures l to ,4.,

ProjectingV into inner shell 4| from the outer end thereof is anopen-ended burner tube 5| carrying a burner nozzle 52 provided' vwithlongitudinally extending air passages 53. Arseriesl of ports 54 foradmitting air from inner shell 4 v and air intake stack 6 is provided attheY open end of burner tube 5|, which is held in place in concentricrelation to inner shell 4| by spacing elements 55. Inner shell Y4| isprovided at its outer end with an upstanding flange registering with butseparated by an asbestos gasket from closure 53, into which is threadeda coupling 5l which receives gas inlet conduit 1. A packing assembly 58occupies the extreme outer end Yof inner shell 4|, the packing-assemblybeing so designed as to ,permitv gas linlet conduit 'l to projecttherethrough into the open end of burner tubeSI.

In operation, gas is admitted through gas inlet conduit I into burnertube 5| and thence through coupling member 43 into heating element 3.Air

yis admitted through' air intake stack 6 tothe This secondary airispre'- Y element 3: these products are returned through end 3b of heatingelement 3 to branch 43h of coupling member 43, proceeding thence throughthe generally annular passage 41 in outer shell 42 to the annular space48 within discharge stack 5.

In both embodiments of the invention, the heating element and fittingare welded or otherwise'sealed in gas-tight relation to each other andto the metal shell of the furnace. For example, an annular flange B0Welded to burner assembly 4 may itself be welded to a collar 6I, thelatter being welded to metal shell 62. In such case, central stiffeningribs 63a, and 63h may be welded to collar BI, thus assisting inpreventing canting of burner assembly 4 under the bending moment imposedby the weight of the heating element at the opposite end of the fitting.The resulting structure obviates the need for alloy metal hangers orrefractory sup ports located in the interior of the furnace,accomplishing the same end from the exterior, and at the same timeeffectively seals the furnace against escape of unburned g'as andproducts of combustion.

In both embodiments, those parts that are subjected to hightemperatures; e. g., the burner tube, burner nozzle, inner shell, outershell, coupling member and heating element, are made of heat-resistantalloy steels such as chrome-nickel steel containing about 25% chromiumand about 12% nickel. As indicated, parts are preferably Welded togetherin gas-tight relation, especially at points where there is danger ofescape of gas or products of combustion. However, these and likeconsiderations are not necessarily of the nature of limiting factors,particularly in the event that some fuel other than gas is used; as amatter of fact, numerous modifications in composition, arrangement andproportions of these and other features may be made without departingfrom the spirit of the invention.

It is intended that the patent shall cover, by suitable expression inthe appended claims, whatever features of patentable novelty reside inthe invention.

I claim:

1. A heat-treating furnace having a peripheral wall; means defining anopening in the wall; a burner tube extending into the opening from apoint outside the wall, said burner tube carrying a burner nozzle at theinner end thereof; a fitting mounted in the opening in surroundingrelation to the burner tube and extending from a point outside the wallto a point inside the wall, said fitting comprising an outer shell thatis substantially concentric with the opening in the wall, an inner shellthat is substantially concentric with the burner tube, and an elbowlocated at the inner end of the inner shell to change the direction oftravel of the eiilux from the burner tube immediately upon its dischargefrom the burner nozzle; and, supported by the fitting itself in closeproximity and substantial parallelism to the wall, a radiant tubeheating element taking the form of a generally oval loop having an inletend on one side of said loop at a point between the ends of said sideand connected in sealed relation to the said elbow located at the innerend of the inner shell and an outlet end adjacent said inlet end andconnected in sealed relation to the inner end of said outer shell, theiiow in all portions of that side of the loop in which said inlet andoutlet ends are disposed being in the same direction and the flow in allportions of the opposite side of the loop being in the oppositedirection.

2. A heat-treating furnace as in claim 1 in which the inner shell issubstantially concentric with the outer shell.

3. A heat-treating furnace as in claim 1 in which the inner shell iseccentric to the outer shell.

4. A heat-treating furnace as in claim 3 in which the inner shell istangent to the outer shell.

5. A heat-treating furnace as in claim 4 in which the point of tangencybetweeen the inner and outer shells is at the siX-oclock position.

6. A heating unit comprising a combustion tube member of generallyelongated oval form having substantially parallel side sections andcurved sections connecting said side sections, said combustion tubemember having one of its side sections provided with adjacent inlet andoutlet ends disposed between said curved sections; a tubular dischargemember connected in sealed relation to and extending from said outletend of said combustion tube member in a direction substantiallyperpendicular to the plane of said combustion tube; a tubular inletmember of smaller cross-sectional area than said discharge member anddisposed within said tubular discharge member, said tubular inlet memberbeing connected in sealed relation at one end. thereof to said inlet endof said combustion tube; and connecting members for holding said tubulardischarge and inlet members in fixed relation to each other.

'7. A heating unit as in claim 6 in which kthe connecting members holdthe discharge and inlet members in concentric relation to each other.

8. A heating unit as in claim 6 in which the connecting members hold thedischarge and inlet members in eccentric relation to each other.

EDWIN A. CORNS.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number Name Date 2,041,930 Houlis May 26, 19362,064,095 Wilson Dec. 15, 1936 2,200,731 Woodson May 14, 1940 2,220,582Ruckstahl Nov. 5, 1940 2,232,272 Rieger Feb. 18, 1941 2,255,540 DreifeinSept. 9, 1941 2,391,447 Edge Dec. 25, 1945

